Protractor



W. D. WEBBER PROTRACTOR Filed Nov. '7, 1950 ATTDRNEYS Patented July 8, 1952 UNITED STATES PAT NT QFFICE.

2,602,228 Y V PROTRACTOR William 1 Webber, Chicago, 111. Application November '7, 1950, Serial No. 192,501

. 1 This invention relates to a'plotting instrument, and more particularly to a protractor.

: Theobject of the invention is to provide-a protractor'which includes a central hub and a ring having several sets of graduated scales, or

markings, thereon, the ring being rotatably connected to the hub, whereby the protractor can conveniently and accurately be used for plotting or making various calculations.

Another object of the invention is to provide a protractor which includes a central, stationary hub and revoluble ring having graduations thereon to enable the user to determine any de-' gree angle by turning the ring not more than 45 from its zero position.

Another object of the-invention is to provide a protractor which is extremely simple and inexpensive to manufacture.

Other objects and advantages will be apparent from the following description.

In the accompanying drawings forming a part of this application, and in which like numerals are used to designate like parts throughout the same:

Figure 1 is a plan view of the protractor constructed according to the present invention;

Figure 2 is a sectional view taken on the line 2-2 of Figure 1;

Figure 3 is an enlarged sectional view showing the sliding connection between the ring and hub;

Figure 4 is a plan view of the protractor of the present invention showing the protractor being used or set for determining an angle.

Referring in detail to the drawings, the numeral l8 designates a stationary hub which may be made of a flexible, transparent, plastic material. The hub l includes a central portion H, and extending from the central portion H is a plurality of arms I2, Figure l. The arms I2 are each provided on their outer end with a groove or slot Hi, Figure 3, for a purpose to be later described.

Rotatably connected to the hub i0 is a ring i5, and the ring is fabricated of a transparent material. The ring has projecting inwardly from its inner periphery a tongue it which slidably rides in the groove |Ll,.so as to effect a rotatable connection between the ring [5 and the hub 0. The central portion ll of the hub i0 is provided with an "opening l'l, whereby a pencil may be readily inserted through the opening l7.

Extending from the outer periphery of the ring l5 and formed integrally therewith are a plurality of pointer elements. These pointer ele- 1 Claim. (Cl. 33-1) mentsare designated by the numerals l8, I9, 20 and 2|, andit will be seen that the pointer elements arespaced apart. The ring I5 is further provided with four rows or sets of graduations or markings on its upper half, and these four rows of scales or markings are designated by the numerals 22, 23, 24 and 25. These four rows of markings, starting with the inner row and reading to the right and to the left from the position zero, represent (1) zero degrees to 90 degrees, (2) 90 degrees to degrees, (3) 180 degrees to 270 degrees, and (4) 270 degrees to p 360 degrees.

From the foregoing it is apparent that a protractor has been provided which comprises the stationary hub l0 and the movable ring [5. The protractcr is designed so that the ring [5 can be either turned to the left or to the right while the hub I0 is held stationary or centered at its zero position. The ring I5 is provided with four rows of graduations 22, 23, 24 and 25, and these graduations are from zero degrees to 360, and appear only on the upper half of the ring I5. The ring 15 has four pointer elements [8, I9, 20 and 2|, which are arranged at 90-degree intervals. Thus, reading to the right from position zero, the distance from element [8 to element I9 is zero degrees to 90, from pointer element I!) to pointer element 20 is 90 to 180, from pointer element'20 to pointer element 2! is 180 to 270, and from pointer element 2| to pointer element I8 is 270 to 360. Conversely, reading to the left from position zero, from pointer element [8 to pointer element 2| is zero degrees to 90, from pointer element 2! to pointer element20 is 90 to 180, from pointer element 20 to pointer element I9 is 180 to 270, and finally, from pointer element IE to pointer element 18 is 270 to 360.

The following examples are for clarification to show how various angles are determined: Moving the ring I5 10 degrees to the right from position zero, the following angles will result: 10, 100, and 280 at pointer elements l8, I9, 20 and 2|, respectively. Conversely, if ring 15 is moved 10 degrees to the left vfrom position zero, the result will be: 10, 100, 190, and 280 at pointer elements l8, 2| 20 and I9. Thus, it is possible to determine any degree angle by turning the ring I5 either to theright or to the left, as the case may be, not more than 45 from position zero. For example, if 70 to the right from position zero is desired, it'can be determined by turning ring l5 20 to the left from position zero, resulting in an angle of 70 to the right from position zero at pointer element [9 (90 minus 20), and further, the result will be 160 to the right at pointer element 20 (180 minus 20), and 250 to the right at pointer element 2| (270 minus 20). All angles are determined from one point (hub l centered at Dosition zero).

The protractor is preferably made of a transparent plastic material, and the hub I0 is com posed of a plastic which is sufiiciently flexible so that the hub and ring can be easily assembled or connected together. In Figure 4, there is shown the simple manner in which a line described in any course can be determined, as per the examples in Figure 4 which shows a course of south 35 west, arrived at by moving ring [5 to the position shown in Figure 4.

I claim:

A protractor comprising astationaryhub iabricated of a flexible transparent material, said hub including a central portion and a plurality of arms extending radially from said central portion; there being an opening in said central portion, the outer end of each of said arms being provided with -a groove, a transparent ring having an inwardly extending tongue slidably positioned in said grooves, a plurality of pointer elements integral with and extending from the outer periphery of said ring and spaced apart, said ring being provided with a plurality of graduated scales thereon.

WILLIAM D. WEBBER.

REFERENCES CITED The following references are cf'record in the file of this patent:

UNITED STATES PATENTS Number Name Date 918,947 Boljahn Apr. 20, 1909 1,346,273 Solar July 13, 1920 1,362,683 Solar Dec. 21, 1920 21,409,303 3 'Lewis Mar. 14, 1922 1,637,933- Galvin Aug. 2, 1927 21903071 Keppers Feb. 13, 1940 2,216,490 Garrett Oct. 1, 1940 2,397,002. Hagner Mar. 19, 1946 2,471,327 Hunt May 24, 1949 2,476,338 Vitez -1. July 19, 1949 

